1. Field of the Invention
The present invention generally relates to stacking sheets of material on a pallet, for example, and, in addition, to exchanging pallets once a sufficient, or predetermined, quantity of sheets has been stacked on the pallet.
2. Description of the Relevant Art
Many materials produced by strip mills, including sheet metal, for example, are typically sold in large, coiled rolls. Those purchasing these large, coiled rolls and desiring to manufacture various products from the sheet metal, for example, often find it necessary to have the sheet metal slit into narrow strips on a slitting line and/or otherwise cut to width. In various circumstances, as a result, the sheet metal is slit longitudinally along the length thereof to sizes suitable for particular products and/or stamping processes, for example. Various exemplary devices and methods for slitting material and/or cutting materials to width are disclosed in U.S. Pat. No. 4,298,633, entitled “METHOD AND APPARATUS FOR TENSIONING METALLIC STRIPS ON A SLITTING LINE”, which issued on Nov. 3, 1981; U.S. Pat. No. 4,614,101, entitled “METHOD OF REWINDING SLIT METAL STRANDS”, which issued on Sep. 30, 1986; U.S. Pat. No. 5,373,766, entitled “SLITTER KNIFE HOLDER”, which issued on Dec. 20, 1994; U.S. Pat. No. 5,421,535, entitled “METHOD AND APPARATUS FOR AUTOMATICALLY WINDING SCRAP METALLIC STRIP METAL”, which issued on Jun. 6, 1995; U.S. Pat. No. 7,134,372, entitled “CNC SLITTER MACHINE”, which issued on Nov. 14, 2006, and U.S. patent application Ser. No. 11/268,004, entitled “COMPENSATING STRIPPER RINGS FOR MATERIAL SLITTING MACHINES”, which was filed on Nov. 7, 2005, the entire disclosures of which are incorporated by reference herein. Other exemplary slitters include HERR-VOSS® STAMCO® STRAND EXTENSIONER® and “Compu-Cut”™ machines available from the Herr-Voss Stamco Company in Callery, Pa.
Further to the above, there are a variety of shape defects that may arise in flat rolled materials, especially in metal materials, for example. Mill induced defects in metal materials can include, for example, wavy edges, center buckles, quarter buckles, crossbow, and coil set. Such shape defects may be caused by misaligned rolls or other substandard equipment or manufacturing processes that can be found in an array of processing lines. Regrettably, material related shape problems result in inefficient operations at downstream processing plants, and material variability or inconsistency can cause production delays, customer dissatisfaction, and many other problems and potential costs. In view of the above, levelers have been developed to reduce such defects and problems and can be employed before the material has been wound into a coiled roll and/or after the material has been unwound from the roll. Various exemplary devices and methods of leveling material are disclosed in U.S. Pat. No. 4,635,458, entitled “LEVELING APPARATUS”, which issued on Jan. 13, 1987; U.S. Pat. No. 4,587,822, entitled “TENSION LEVELING APPARATUS”, which issued on May 13, 1986; U.S. Pat. No. 4,765,169, entitled “METHOD OF TENSION LEVELING NONHOMOGENEOUS METAL SHEET”, which issued on Aug. 23, 1988; U.S. Pat. No. 5,255,549, entitled “TENSION LEVELER ROLL CLEANING SYSTEM AND METHOD”, which issued on Oct. 26, 1993; and U.S. patent application Ser. No. 11/149,898, entitled “CNC LEVELER”, which was filed on Jun. 10, 2005, the entire disclosures of which are incorporated by reference herein. Other exemplary levelers include HERR-VOSS® STAMCO® PRECISION LEVELER® machines available from the Herr-Voss Stamco Company in Callery, Pa.
Once the material has been unwound from their large, coiled rolls and sufficiently leveled and cut to width, if necessary, the material can be cut into sheets. In various circumstances, sheet metal, for example, can be fed into a shear, or cut-to-length line, and cut lattitudinally in order to cut the sheet metal to length. Depending on various parameters such as the speed of the line, the length of the sheets, and the thickness of the material, for example, a shear may often comprise a down cut shear, a rotary shear, and/or a hydraulic shear. Exemplary cut-to-length processing lines are available from the Hen-Voss Stamco Company in Callery, Pa. Once cut to length, the sheets can be stacked onto a pallet and, after a sufficient, or predetermined, quantity of sheets has been stacked on the pallet, the finished pallet can be removed from the processing line. In many circumstances, though, it is the removal of the finished, stacked pallet and the placement of an empty pallet that causes interruptions in the processing of the material. What is needed is a sheet stacking device which can decrease and/or eliminate such interruptions.